Three-piece, wound-core golf balls with balata (trans-polyisoprene) covers are typically preferred by professional and low handicap amateur golfers. These balls provide a combination of distance, high spin rate, and control that is not available with other types of golf balls. However, balata is easily damaged in normal play, and thus lacks the durability required by the average golfer.
Two-piece golf balls, which are typically used by the amateur golfers, provide a combination of durability and maximum distance that is not available with balata covered balls. These balls include a core, formed of a solid sphere which typically includes a polybutadiene-based compound, encased in an ionomer cover, such as SURLYN.RTM.. Golf ball cover ionomers are, typically, copolymers of an olefin and an unsaturated carboxylic acid in which at least a portion of the carboxylic acid groups have been neutralized with a metal ion, typically sodium or zinc. These balls are extremely durable, have good shear resistance, and are difficult to cut. However, this durability results from the hardness of the ionomer, which gives such balls a very hard "feel" when struck, which many golfers find inferior to the softer "feel" of a balata covered ball. In addition, the hardness of the ionomer gives the balls a lower spin rate, making these balls more difficult to control during short-distance hitting.
A basic discussion of conventional ionomers is found in the Polymeric Materials Encyclopedia, "Ionomers (Overview)," at pp. 3435-3454 (Ed. by J. Salamone, 1996). See also M. R. Tant, et al., Eds., "Ionomers," pp. 3-40 and 197-203 (1997). Generally speaking, ionomers have either a cationic or anionic group attached as a pendant group to the polymer backbone. Ionomers contain acidic groups, such as carboxylate or sulfonate, or basic groups, such as quaternary nitrogen, the acidic or basic groups being at least partially neutralized with a conjugate acid or base. Negatively charged acidic groups, such as carboxyl or sulfonate, may be associated with a cation, such as a metal ion. Positively charged basic groups, such as quaternary nitrogen, are generally associated with an anion, such as a halide, an acetate ion, or the like.
Many attempts have been made to produce a golf ball with the control and feel of a wound balata ball, and the durability of an ionomer covered two-piece ball. These attempts have focused largely on modifying the properties of ionomer compositions by forming ionomer blends. For example, U.S. Pat. Nos. 4,884,814, 5,120,791, 5,324,783, 5,415,937 and 5,492,972 disclose ball compositions that are blends of high-hardness ionomers and low-hardness ionomers.
U.S. Pat. No. 5,692,974 discloses compositions using cationic ionomer polymers having positively charged quaternary ammonium groups. The cationic groups, preferably present in cationic polyurethane polymers, impart improved characteristics to golf ball covers formed therefrom.
Other types of polymers, such as ionenes and zwitter-ion polymers, have been formulated and used in a variety of applications [See, e.g., K. Hwang et al., "Properties of Polyether-Polyurethane Zwitterionomers," Polymer Engineering & Sci., 21(15): 1027-1035 (Oct. 1981). Synthesis of five- and six-membered cyclic sulfonium zwitter-ions, for example, is generally accomplished by reaction of a phenolic compound with tetrahydrothiophene-1-oxide and hydrogen chloride. The salts of hydrogen chloride are then prepared and reacted with an anion exchange resin such as DOWEX 1 in the hydroxyl form or sodium methoxide to form the zwitter-ion structure. [M. Hoover et al., "Recent Advances in Ion-Containing Polymers," J. Polymer Sci., 45:1-37 (1974)].
Ampholytic polymers having a zwitter-ionic nature, for example, are known for use in soil conditioners, for recovery of minerals from aqueous suspensions, as flocculants, in shampoos, in hair conditioners, in paper fortifiers, in pigment-retention aids, as isoelectric focusing of proteins, as substitutes for proteins and gelatin substrates of photographic film. [J. Salamone et al., "Polyampholytes," Encyclopedia of Polymer Science and Engineering, Vol. 11, pp. 514-530 (2nd ed., 1988)]. Some of these ionenes and zwitter-ion polymers are described below.
U.S. Pat. Nos. 3,931,319 and 4,027,020 and EP 827,690 A2 disclose anti-microbial polymeric quaternary ammonium compounds (ionenes) having linear chains that randomly terminate in quaternary ammonium moieties, i.e., the ammonium is part of the polymeric chains rather than being appended thereto. Similarly, U.S. Pat. Nos. 3,874,870 and 4,025,627 disclose microbicidally active compounds including condensation products of 1,4-dihalo-2-butene with either difunctional tertiary amines of R'R"N-Z-N-R'R" or 1,4-bis-dimethylamino-2-butene, respectively, for use in cosmetic or aqueous compositions, respectively.
U.S. Pat. No. 4,046,750 discloses linear ionene polyquaternary cationic polymeric segments bonded by quaternization to biocompatible, small, porous particles containing halide or tertiary amine sites to which the segments attach. These particles, or beads, offer a positively-charged surface area for irreversibly binding polyanions, such as heparin, DNA, RNA, or bile acids, to remove them from solution or for reversibly binding monoanions, such as penicillin, pesticides, sex attractants, and the like for slow release.
U.S. Pat. No. 4,217,914 discloses a quaternized polymer for use as a hair or skin cosmetic agent, such as shampoo or lotion, having recurring units of RR'N.sup.+ X.sup.- A-RR'N.sup.+ X.sup.- B. Also disclosed are the use of such polymers for protecting hair and as pesticidal agents, flocculation agents, surfactants, and ion exchange agents.
U.S. Pat. No. 4,506,081 discloses novel polyquaternary ammonium compounds prepared from N,N'-bis(dialkylaminoalkyl)ureas, hydrochloric acid, epichlorohydrin, and tertiary amines for use as herbicides, corrosion inhibitors, debonding agents, flocculants, softeners, anti-static agents, and demulsifiers.
Despite the efforts noted above to produce improved golf balls, materials capable of providing improved properties, such as ionenes or zwitter-ion polymers, do not appear to be used in golf ball compositions. There is a need for new golf ball compositions capable of providing improved performance, such as an increased initial velocity, and having an improved feel during use thereof.